The present invention relates to a slide-driving device for knuckle presses used primarily in cold forging operations such as sizing and precision extrusion.
Examples of conventional presses used in cold forging include crank presses, link presses, and knuckle presses. Since each of these presses has advantages and disadvantages with regard to molding, these presses are used selectively according to the product to be worked on. In particular, knuckle presses provide a high molding load around the bottom dead center. This has encouraged their use in cold forging.
Japanese laid-open patent publication number 60-24300 presents an example of a slide-driving device for knuckle presses based on conventional technology. Knuckle presses that receive thrust force with a plunger and plunger guide disposed on a frame have also been proposed.
In the slide-driving devices for knuckle presses described above, the lower link, which connects to the slide and raises and lowers the slide, is frequently tilted to a large angle. This makes such knuckle presses inappropriate for extrusion and the like due to the fact that the slide slopes at an angle when thrust force is generated. Also, in knuckle presses that absorb the thrust force with a plunger and a plunger guide, the plunger guide gap becomes larger than the slide guide gap, making this arrangement impractical.
When high-precision is required in the products, fine compensation is required to offset changes in the bottom dead center of the slide, which can be affected by temperature changes in the machine or die. Conventional methods of performing the compensation, by adjusting the bottom dead center of the slide by manually or electronically rotating a nut in a prescribed direction, makes fine adjustments difficult and fails to provide a product with reliably high precision.